It's a throwaway reference, but nevertheless notable in that it's yet another of the things that brings the current Marvel Universe more into line with the movies based on it: In this week's Avengers Assemble #9 by Kelly Sue DeConnick and Stefano Caselli, Dr. Bruce Banner (better known to fans as The Incredible Hulk), cites the practice of hydraulic fracturing (colloquially referred to as "fracking" as a "Band-Aid solution" that created as many problems as it solves.

Even while the line makes sense in context and isn't a big part of the story, it's hard not to take the inclusion of fracking as a wink-and-a-nod to Mark Ruffalo, the actor who played Banner in Marvel's The Avengers and who is a prominent and outspoken opponent of fracking. In December, he offered fans a chance to bid on eBay to accompany him to the premiere of The Avengers, with the winning bid going to a non-profit organization opposed to the practice.

“The great thing about the Avengers and our superhero mythology is that they are people that fight for the common man over impossible odds, and for the betterment of the whole,” Ruffalo said in an interview last November about his fracking protests. “So in some ways, that whole mythology feeds into what I’m trying to do here.”

The month after that interview, Ruffalo joined a group delivering water to a small town in Pennsylvania. Dimock Township's water supply had been contaminated by a fracking accident and after the government determined that the pollutants were sufficiently dispersed to make the water safe, locals continued reporting odors, discoloration and other problems, so anti-fracking activists delivered truckloads of fresh water to the area.